Assessing the Role of Endophytic Fungi in Canada Wildrye Grass

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Dr. Thomas Bultman, Biology

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Endophytes are microbial species that live within a plant asymptomatically. Some fungal endophytes have developed a symbiotic relationship with cool-season grasses. It has been suggested that these symbiotic fungi cooperate in a defensive mutualism with their host grasses by producing alkaloids. The alkaloids deter various types of herbivores. The objective of this study was to determine the level of mutualism present in these relationships, and whether different endophyte isolates influence the level of mutualism. Specifically, we examined the effect these endophytic fungi exert on insect abundance, insect herbivory, and plant growth in Canada Wild Rye (Elymus canadensis), a grass native to North America. Seeds were collected from Carleton College Prairie in Northfield, Minnesota. These seeds consisted of several experimental groups: those naturally uninfected, those naturally infected, and those artificially disinfected with Epichloe canadensis. These groups were studied in both outdoor and indoor laboratory trials. As a bioassay for alkaloid activity, we utilized Bird-Cherry Oat Aphids (Rhopalosiphum padi). In the field experiment, twenty-four plants were assigned to a treatment group, and insects were collected via vacuum sampling. Visual estimates of herbivore damage were performed. In the indoor aphid bioassay, twenty-five plants were assigned to each treatment group and apterous aphids were placed on grasses, and scored for survival and reproductive success. These experiments were performed during 2015 and 2016. In the 2015 bioassay experiment, fewer aphids were present on grasses with endophyte infection. This result was mirrored in the field experiment when feeding by sucking insects was analyzed. In the 2016 bioassay, we found that removal of endophyte from grasses made them more susceptible to aphids. Contrary to our expectations, the presence of endophytic fungi did not enhance plant growth in the field experiment for either year.

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